1. Field of the Invention
The present invention relates to a trigger coil for generating a trigger voltage to be applied to a trigger electrode of a flashlight emitting tube.
2. Description of the Related Art
Hitherto, there is known a camera in which when a subject brightness is insufficient, a photography is performed while a flashlight is emitted in synchronism with a shutter operation. Such a camera is provided with a flashlight generating circuit for generating a flashlight. The flashlight generating circuit comprises a booster circuit, a main capacitor for storing an electric power boosted by the booster circuit, a flashlight emitting tube for emitting a flashlight by the electric power emanated from the main capacitor, and a trigger coil for generating a trigger voltage to be applied to a trigger electrode of the flashlight emitting tube.
The trigger coil comprises a primary winding, a secondary winding and a package incorporating both the primary winding and the secondary winding. For example, the number of turns of the primary winding and the number of turns of the secondary winding are 20 turns and 500 turns, respectively. And a diameter of the primary winding and a diameter of the secondary winding are "PHgr"0.2 and "PHgr"0.05, respectively.
In the trigger coil as mentioned above, there are two types of trigger coil one of which is directed to a four-terminal type of trigger coil having total four terminals consisting of two terminals of the primary winding and two terminals of the secondary winding, and another being directed to a three-terminal type of trigger coil having total three terminals consisting of a common terminal in which one end of the primary winding is connected to one end of the secondary winding on a common basis and two terminals of the primary winding and the secondary winding. Particularly, in case of the threeterminal type of trigger coil, the primary winding, which is relatively large in diameter, and the secondary winding, which is relatively small in diameter, are wound at the same place of the common terminal and are mounted on a circuit substrate by soldering. This involves such a problem that the slight external force disconnects the secondary winding, which is relatively small in diameter.
In view of the foregoing, it is an object of the present invention to provide a trigger coil intended to preventing disconnection of the secondary winding.
To achieve the above-mentioned object, the present invention provides a trigger coil comprising a primary winding, a secondary winding, a package incorporating therein both the primary winding and the secondary winding, a common terminal to which one end of the primary winding and one end of the secondary winding are connected, a primary terminal to which another end of the primary winding is connected, and a secondary terminal to which another end of the secondary winding is connected, wherein a current conducts between the primary terminal and the common terminal to generate on the secondary terminal a trigger voltage to be applied to a trigger electrode of a flashlight emitting tube, characterized in that
said common terminal has a pin-like shape extending to pass through the package, one end of which is connected to a circuit substrate, and
one end of the primary winding is connected to an exit portion of said common terminal from the package at a side to be connected to the circuit substrate, and one end of the secondary winding is connected to an exit portion of said common terminal from the package at a side apart from the circuit substrate.
An important feature of the trigger coil of the present invention resides in the point that one end of the primary winding is connected to an exit portion of said common terminal at a side to be connected to the circuit substrate, and one end of the secondary winding is connected to an exit portion of said common terminal at a side apart from the circuit substrate. Even if the trigger coil is mounted on the circuit substrate and the external force is applied thereto, as compared with a conventional trigger coil in which a primary winding involved in the larger diameter and a secondary winding involved in the smaller diameter are wound on the same place of the common terminal, it is expected that an affect of the external force onto one end of the secondary winding is small. Thus, it is possible to prevent a disconnection of the secondary winding.